Digital transmitters and digital power amplifiers have been an active area of research these days with the advance of CMOS technology. Energy-efficient small transmitter is critical for many applications that employs MIMO, multiband, and multi-standard transceivers because of multiple transmitters being adopted in a single chip or system. Each conventional transmitter consists of baseband digital-to-analog converter (DAC), filter, upconversion mixer, and driving/power amplifier, and occupies a large area and consumes static current in its amplifiers when outputting even a small power. For instance, a mobile system for multi-band, MIMO radio that supports multiple standards, such as Wi-Fi, Bluetooth, and cellular, consumes a very large chip area and high power with many analog/RF blocks that draw very high current. Digital transmitters integrate all block in a transmitter chain in a single block that directly generates modulated RF signal without any high static current. On the other hand, a very linear transmitter with excellent EVM and wide bandwidth is also desired to support a very high data throughput in modern wireless standards such as 5G or 802.11ax.
This disclosure presents linearity enhancement techniques related to phase distortion for digital wireless transmitters, digital power amplifiers, RF digital-to-analog converters (RF DAC), and/or digital-to-RF converters.
This section provides background information related to the present disclosure which is not necessarily prior art.